Dorset’s Habitats – wild heathlands
Colin Varndell looks at a habitat in which Dorset is rich, but in which the country and indeed the world is poor
Published in August ’12
In times gone by, Dorset’s wild heathlands were considered little more than bare wastelands. Sadly, it was not until these places of raw, untamed natural beauty had been seriously fragmented that their environmental importance was realised.
The geology of the Poole basin largely comprises nutrient-deficient coarse sands, gravels and clays. All of Dorset’s heathlands were once covered in high temperate forest. The deforestation of this area began in earnest during the Bronze Age and continued right up until the middle of the last century. As the tree cover was removed, so the nutrients in the surface soils were readily washed or leached down through the free draining gravels, leaving a highly acidic surface allowing plants like gorse, heather, bog myrtle and Scots pine to take over and dominate the landscape. The change from high forest to lowland heath has been documented by an increase in heather and grass pollen preserved in peat bogs at the expense of tree pollen. Just about all the wildlife which thrives here is at least uncommon if not internationally rare. In fact, the heathlands of the Poole basin are among the rarest habitat types in the world.
The plantlife is predominantly heather, with smatterings of bog asphodel and cotton grass occurring in the wetter areas. During summer such rarities as marsh gentian and bog orchid can be found, and around the edges of the bogs insectivorous sundew plants grow. These fascinating little plants exist in the poorest of conditions, and have evolved to gain their nutrients from insects. The upper surface of the plant’s leaves are covered with red tentacles which secrete a sticky mucilage. Insects, attracted to the bright red colour of the plant, become stuck on the tentacles. The plant uses enzymes to dissolve insects and to extract nitrates and other nutrients from their bodies.
In high summer, two specific butterflies are found on Dorset’s heathlands. The grayling, master of disguise, displays a motley, camouflage pattern on the underwing. When the insect comes to rest it tucks its forewing behind the hindwing and tilts its wings to prevent a telltale shadow, thus making it almost impossible to detect. The silver-studded blue, although rare elsewhere, can be hugely abundant on the heaths, often with several insects flying up from every clump of heather as you pass by. These attractive butterflies frequently settle on the heather late in the day, spreading their wings to soak up the weakening rays of the evening sun. The emperor moth is Britain’s only silk moth and can be found on the Dorset heaths. Males fly by day but are difficult to spot as they are very fast insects, and you may only notice an orange blur as one passes. Female emperor moths remain still during daytime, patiently waiting on heather or gorse for the males to find them.
Dragonflies are the top predators of the heathland insect world, feeding on small airborne insects. They hold their bristly legs in front of them to form a basket shape into which prey is captured. Notable species specific to the Dorset heaths include the downy emerald, which is a medium sized dragonfly of metallic appearance, and the hairy dragonfly. Both of these insects are early summer species occurring in May and June. Later in the summer, emperor, four spotted chaser and migrant hawker are on the wing. It can be fascinating to watch them darting in and out of the sunbeams attacking the columns of gnats on a summer afternoon.
Wild mammals are not abundant on the heaths, but rabbit, fox and roe deer are occasionally seen. The animal you are most likely to encounter is the sika deer. It is widely believed that the original Dorset Sika were escapees from a herd which had been introduced to Brownsea Island in the 1870s. Some of these animals left the island by wading across to the mainland at low tide, establishing a colony on the saltmarsh and eventually spreading to the heaths and woods of east Dorset.
Dartford warblers, synonymous with heathland, are present all year, flitting incessantly between the gorse bushes in their tireless search for insects. Stonechats and meadow pipits are also permanent residents. Summer visitors include two heathland specialists, the nightjar and hobby. Hobbies may be seen hunting dragonflies or other large insects, nightjars are moth catchers and hunt around dusk.
The smooth snake is Britain’s rarest native reptile and has its stronghold on the heathlands of east Dorset and the New Forest. The smooth snake gets its name from the unkeeled scales of its body, which are completely flat. This reptile is one of the most difficult wild animals to observe as it rarely basks out in the open like an adder or grass snake does, but rather entwines itself through dense vegetation.
The sand lizard is rare elsewhere in the country, but here, on these Dorset heaths, it is common. The male sand lizard is stunningly attractive, especially during the breeding season in early summer when its green markings intensify. Look for these robust lizards on sunny banks at the end of the day where they will be soaking up the dying embers of the sun’s warmth.
It is the sheer wildness of lowland heath that makes one feel totally immersed in the natural world. On cold winter mornings ghostly mists drift over the bogs and pools. In spring the heath erupts in a mosaic of white blackthorn and yellow gorse. When the heather is in bloom in summer, the landscape is transformed with shades of pink and mauve, and in autumn as the silver birch trees and bracken change to golden yellow the heath is arguably at its most spectacular.
The county of Dorset is unique because of its fantastic range of wild habitats to explore. But none (neither here in Dorset, nor indeed anywhere else in Britain) reveals such a wealth of rarities as the lowland heaths of the Poole basin.